"""
自定义分页组件,以后如果想要使用这个分页组件，您需要做如下几件事：

在视图函数中：
def lh(request):
    # 1.根据自己的情况从数据库筛选自己想要的数据
    queryset = lianghao.objects.all()

    # 2.实例化分页对象
    page_object = Pagination(request,queryset)
    context={
        "search_data": search_data,
        "queryset": page_object.page_queryset,  # 分页完的数据
        "page_string":page_object.html(),       # 生成页码
    }
    return render(request, "lh.html",context)

在HTML页面中：
    {% for obj in queryset %}
        {{ obj.xx }}  来展示数据
    {% endfor %}

    <ul class="pagination">
        {{ page_string }}
    </ul>
"""
from django.utils.safestring import mark_safe

class Pagination(object):
    def __init__(self,request,queryset,page_size=10,page_param="page",plus = 5):
        """
        request：请求的对象
        queryset：符合条件的数据（根据这个数据给他进行分页处理）
        page_size=10：每页显示多少条数据
        page_param="page"：在URL中传递的获取分页的参数，例如:/pretty/list/?page=xx和HTML中name所定义的值
        plus = 5：显示当前页的，前几页和后几页
        """
        from django.http.request import QueryDict
        import copy
        query_dict = copy.deepcopy(request.GET)
        query_dict._mutable = True
        self.query_dict = query_dict

        self.page_param = page_param
        #获取当前页
        page = request.GET.get(page_param, "1")
        if page.isdecimal():
            page = int(page)
        else:
            page = 1
        self.page = page
        self.page_size = page_size
        # 1.根据用户想要访问的页码数，计算出要展示数据的起始位置；page_size=10默认每页展示10条数据；当传递进来参数为7页时，需要展示70-
        self.start=(page - 1) * page_size
        self.end = page * page_size

        self.page_queryset = queryset[self.start:self.end]

        # 计算出总页码,通过统计数据库总行数
        total_count = queryset.count()
        total_page_count, div = divmod(total_count, page_size)
        if div:
            total_page_count += 1
        self.total_page_count=total_page_count
        self.plus = plus


    def html(self):
        # 计算出，显示当前页的前5页、后5页
        if self.total_page_count <= 2 * self.plus + 1:
            start_page = 1
            end_page = self.total_page_count
        else:
            # 如果数据数据较多时，> 11页

            # 当前页<5页时
            if self.page <= self.plus:
                start_page = 1
                end_page = 2 * self.plus + 1
            else:
                # 当前页 >5
                # 当前页+5 大于总页面
                if (self.page + self.plus) > self.total_page_count:
                    start_page = self.total_page_count - 2 * self.plus
                    end_page = self.total_page_count
                else:
                    start_page = self.page - self.plus
                    end_page = self.page + self.plus

        # 页码
        page_str_list = []

        # 首页
        self.query_dict.setlist(self.page_param, [1])
        page_str_list.append('<li><a href="?{}">首页</a></li>'.format(self.query_dict.urlencode()))

        # 上一页
        if self.page > 1:
            self.query_dict.setlist(self.page_param, [self.page - 1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [self.page])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)

        #页面
        for i in range(start_page, end_page + 1):
            self.query_dict.setlist(self.page_param, [i])
            if i == self.page:
                ele = '<li class="active"><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            else:
                ele = '<li><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            page_str_list.append(ele)

        # 下一页
        if self.page < self.total_page_count:
            self.query_dict.setlist(self.page_param, [self.page + 1])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [self.total_page_count])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)

        # 尾页
        self.query_dict.setlist(self.page_param, [self.total_page_count])
        page_str_list.append('<li><a href="?{}">尾页</a></li>'.format(self.query_dict.urlencode()))

        search_string = """
            <li>
                <form method="get" style="float: left;margin-left: -1px">
                    <div class="input-group" style="width: 110px">
                        <input type="text" name="page" class="form-control" placeholder="页码">
                        <span class="input-group-btn">
                            <button  type="submit" class="btn btn-default">跳转</button>
                        </span>
                    </div>
                </form>
            </li>
            """
        page_str_list.append(search_string)
        page_string = mark_safe("".join(page_str_list))
        return page_string








